Hydrocarbon dehydrogenation with a multimetallic catalytic composite

ABSTRACT

Dehydrogenatable hydrocarbons are dehydrogenated by contacting them, at dehydrogenation conditions including a hydrogen-rich and substantially water-free environment, with a catalytic composite comprising a combination of catalytically effective amounts of a platinum group component, a Group IVA metallic component, and a lanthanide series component with a porous carrier material. A specific example of the catalyst used in the disclosed hydrocarbon dehydrogenation method in a nonacidic catalytic composite comprising a combination of a platinum group component, a Group IVA metallic component, a lanthanide series component, and an alkali or alkaline earth component with a porous carrier material in amounts sufficient to result in a composite containing about 0.01 to about 2 wt. % platinum group metal, about 0.01 to about 5 wt. % Group IVA metal, about 0.1 to about 5 wt. % alkali metal or alkaline earth metal, and having an atomic ratio of lanthanide series metal to platinum group metal of about 0.1:1 to 1.25:1. A preferred modifying component for the disclosed catalytic composites in a sulfiding reagent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of my prior, copending andnow abandoned application Ser. No. 758,286 filed Jan. 10, 1977; which inturn is a continuation-in-part of my prior application Ser. No. 626,151filed Oct. 28, 1975 and issued Jan. 18, 1977 as U.S. Pat. No. 4,003,826,which in turn is a continuation-in-part of my prior application Ser. No.422,464 filed Dec. 6, 1973 and issued Oct. 28, 1975 as U.S. Pat. No.3,915,845. All of the teachings of these prior applications arespecifically incorporated herein by reference.

The subject of the present invention is, broadly, an improved method fordehydrogenating a dehydrogenatable hydrocarbon in a hydrogen-richenvironment to produce a hydrocarbon product containing the same numberof carbon atoms but fewer hydrogen atoms. In another aspect, the presentinvention involves a method of dehydrogenating normal paraffinhydrocarbons containing 4 to 30 carbon atoms per molecule to thecorresponding normal mono-olefin with minimum production of sideproducts. In yet another aspect, the present invention relates to anovel nonacidic multimetallic catalytic composite comprising acombination of catalytically effective amounts of a platinum groupcomponent, a Group IVA metallic component, a lanthanide seriescomponent, and an alkali or alkaline earth component with a porouscarrier material. This nonacidic composite has highly beneficialcharacteristics of activity, selectivity and stability when it isemployed in a hydrogen-rich environment in the dehydrogenation ofdehydrogenatable hydrocarbons such as aliphatic hydrocarbons, naphthenehydrocarbons, and alkylaromatic hydrocarbons.

The conception of the present invention followed from my search for anovel catalytic composite possessing a hydrogenation-dehydrogenationfunction, a controllable cracking function, and superior conversion,selectivity, and stability characteristics when employed in hydrocarbonconversion processes that have traditionally utilized dual-functioncatalytic composites in a hydrogen-rich environment. In my priorapplications, I disclosed a significant, finding with respect to amultimetallic catalytic composite meeting these requirements. Morespecifically, I determined that a combination of a Group IVA metal and alanthanide series metal can be utilized, under certain conditions, tobeneficially interact with the platinum group component of adual-function catalyst with a resulting marked improvement in theperformance of such a catalyst. Now I have ascertained that a catalyticcomposite, comprising a combination of catalytically effective amountsof a platinum group component, a Group IVA metallic component, and alanthanide series component with a porous carrier material can havesuperior activity, selectivity, and stability characteristics when it isemployed in a dehydrogenation process using a hydrogen-rich environmentif these components are uniformly dispersed in the porous carriermaterial in the amounts and oxidation states specified hereinafter. Ihave also found that a preferred modifying component for this lastcatalytic composite when it is used in hydrocarbon dehydrogenationservice in a hydrogen-rich environment is a sulfiding reagent. I havediscerned, moreover, that a particularly preferred multimetalliccatalytic composite of this type contains not only a platinum groupcomponent, a Group IVA metallic component, and a lanthanide seriescomponent, but also an alkali or alkaline earth component in an amountsufficient to ensure that the resulting catalyst is nonacidic.

The dehydrogenation of dehydrogenatable hydrocarbons is an importantcommercial process because of the great and expanding demand fordehydrogenated hydrocarbons for use in the manufacture of variouschemical products such as detergents, plastics, synthetic rubbers,pharmaceutical products, high octane gasolines, perfumes, drying oils,ion-exchange resins, and various other products well known to thoseskilled in the art. One example of this demand in in the manufacture ofhigh octane gasoline by using C₃ and C₄ mono-olefins to alkylateisobutane. Another example of this demand is in the area ofdehydrogenatin of normal paraffin hydrocarbons to produce normalmono-olefins having 4 to 30 carbon atoms per molecule. These normalmono-olefins can, in turn, be utilized in the synthesis of a vast numberof other chemical products. For example, derivatives of normalmono-olefins have become of substantial importance to the detergentindustry where they are utilized to alkylate an aromatic, such asbenzene, with subsequent transformation of the product arylalkane into awide variety of biodegradable detergents such as the alkylaryl sulfonatetypes of detergents which are most widely used today for household,industrial, and commercial purposes. Still another large class ofdetergents produced from these normal mono-olefins are the oxyalkylatedphenol derivatives in which the alkylphenol base is prepared by thealkylation of phenol with these normal mono-olefins. Still another typeof detergents produced from these normal mono-olefins are thebiodegradable alkylsulfonates formed by the direct sulfation of thenormal mono-olefins. Likewise, the olefin can be subjected to directsulfonation with sodium bisulfite to make biodegradable alkylsulfonates.As a further example, these mono-olefins can be hydrated to producealcohols which then, in turn, can be used to produce plasticizers and/orsynthetic lube oils.

Regarding the use of products made by the dehydrogenation ofalkylaromatic hydrocarbons, they find wide application in the petroleum,petrochemical, pharmaceutical, detergent, plastic, and the likeindustries. For example, ethylbenzene is dehydrogenated to producestyrene which is utilized in the manufacture of polystyrene plastics,styrene-butadiene rubber, and the like products. Isopropylbenzene isdehydrogenated to form alpha-methylstyrene which, in turn, isextensively used in polymer formation and in the manufacture of dryingoils, ion-exchange resins, and the like materials.

Responsive to this demand for these dehydrogenation products, the arthas developed a number of alternative methods to produce them incommercial quantities. One method that is widely utilized involves theselective dehydrogenation of a dehydrogenatable hydrocarbon bycontacting the hydrocarbon with a suitable catalyst at dehydrogenationconditions. As is the case with most catalytic procedures, the principalmeasure of effectiveness for this dehydrogenation method involves theability to perform its intended function with minimum interference ofside reactions for extended periods of time. The analytical terms usedin the art to broadly measure how well a particular catalyst performsits intended functions in a particular hydrocarbon conversion reactionare activity, selectivity, and stability, and for purposes of discussionhere, these terms are generally defined for a given reactant as follows:(1) activity is a measure of the catalyst's ability to convert thehydrocarbon reactant into products at a specified severity level whereseverity level means the specific reaction conditions used--that is, thetemperature, pressure, contact time, and presence of diluents such as H₂; (2) selectivity usually refers to the amount of desired product orproducts obtained relative to the amount of the reactant charged orconverted; (3) stability refers to the rate of change with time of theactivity and selectivity parameters--obviously the smaller rate implyingthe more stable catalyst. More specifically, in a dehydrogenationprocess, activity commonly refers to the amount of conversion that takesplace for a given dehydrogenatable hydrocarbon at a specified severitylevel and is typically measured on the basis of disappearance of thedehydrogenatable hydrocarbon; selectivity is typically measured by theamount, calculated on a mole percent of converted dehydrogenatablehydrocarbon basis, of the desired dehydrogenated hydrocarbon obtained atthe particular activity or severity level; and stability is typicallyequated to the rate of change with time of activity as measured bydisappearance of the dehydrogenatable hydrocarbon and of selectivity asmeasured by the amount of desired dehydrogenated hydrocarbon produced.Accordingly, the major problem facing workers in the hydrocarbondehydrogenation art is the development of a more active and selectivecatalytic composite that has good stability characteristics.

I have now found a multimetallic catalytic composite which possessesimproved activity, selectivity, and stability when it is employed in amethod for the dehydrogenation of dehydrogenatable hydrocarbons in ahydrogen-rich environment. In particular, I have determined that the useof a multimetallic catalyst, comprising a combination of catalyticallyeffective amounts of a platinum group component, a Group IVA metalliccomponent, and a lanthanide series component with a porous refractorycarrier material, can enble the performance of a hydrocarbondehydrogenation method to be substantially improved if the metalliccomponents are uniformly dispersed throughout the carrier material inthe amounts specified hereinafter, if their oxidation states arecarefully controlled to be in the states hereinafter specified and ifthe catalyst is used in a hydrogen-rich and substantially water-freeenvironment. Moreover, particularly good results are obtained when thiscomposite is combined with an amount of an alkali or alkaline earthcomponent sufficient to ensure that the resulting catalyst is nonacidicand utilized to produce dehydrogenated hydrocarbons containing the samecarbon structure as the reactant hydrocarbon but fewer hydrogen atoms.This nonacidic composite is particularly useful in the dehydrogenationof long chain normal paraffins to produce the corresponding normalmono-olefin with minimization of side reactions such as skeletalisomerization, aromatization, cracking and polyolefin formation. In sum,the present invention involves the significant finding that acombination of a Group IVA metallic component and a lanthanide seriescomponent can be utilized under the circumstances specified herein tobeneficially interact with and promote a hydrocarbon dehydrogenationcatalyst containing a platinum group component and, in an especiallypreferred case, an alkali or alkaline earth component.

It is, accordingly, one object of the present invention to provide anovel method for the dehydrogenation of dehydrogenatable hydrocarbons ina hydrogen-rich and substantially water-free environment utilizing amultimetallic catalytic composite comprising catalytically effectiveamounts of a platinum group component, a Group IVA metallic component,and a lanthanide series component combined with a porous carriermaterial. A second object is to provide a novel nonacidic catalyticcomposite having superior performance characteristics when utilized in adehydrogenation process employing a hydrogen-rich and substantiallywater-free reaction environment. Another object is to provide animproved method for the dehydrogenation of normal paraffin hydrocarbonsto produce normal mono-olefins which method minimizes undesirable sidereactions such as cracking, skeletal isomerization, polyolefinformation, disproportionation and aromatization.

In brief summary, one embodiment of the present invention involves amethod for dehydrogenating a dehydrogenatable hydrocarbon whichcomprises contacting the hydrocarbon at dehydrogenation conditionsincluding a hydrogen-rich and substantially water-free environment witha multimetallic catalytic composite comprising a porous carrier materialcontaining a uniform dispersion of catalytically effective amounts of aplatinum group component, a Group IVA metallic component and alanthanide series component. Moreover, substantially all of the platinumgroup component is present in the composite in the elemental metallicstate and substantially all of the Group IVA metallic and lanthanideseries components are present in the composite in an oxidation stateabove that of the corresponding elemental metal. These components areused in amounts, calculated on a wt. % of finished catalytic compositeand an elemental basis, sufficient to result in the composite containingabout 0.01 to about 2 wt. % platinum group metal, about 0.01 to about 5wt. % Group IVA metal and an atomic ratio of lanthanide series metal toplatinum group metal of about 0.1:1 to about 1.25:1.

A second embodiment relates to the dehydrogenation method described inthe first embodiment wherein the dehydrogenatable hydrocarbon is analiphatic compound containing 2 to 30 carbon atoms per molecule.

A third embodiment involves the dehydrogenation method described in thefirst or second embodiment wherein the catalytic composite used thereinis sulfided in an amount sufficient to incorporate about 0.01 to about 1wt. % sulfur, calculated on an elemental basis.

A fourth embodiment comprehends a nonacidic catalytic compositecomprising a porous carrier material having uniformly dispersed thereincatalytically effective amounts of a platinum group component, a GroupIVA metallic component, a lanthanide series component, and an alkali oralkaline earth component. These components are preferably present inamounts sufficient to result in the catalytic composite containing,calculated on a wt. % finished catalytic composite and on an elementalbasis, about 0.01 to about 2 wt. % platinum group metal, about 0.1 toabout 5 wt. % of the alkali metal or alkaline earth metal, about 0.01 toabout 5 wt. % Group IVA metal and an atomic ratio of lanthanide seriesmetal to platinum group metal of about 0.1:1 to about 1.25:1. Inaddition, substantially all of the platinum group component is presentin the elemental metallic state, substantially all of the Group IVAmetallic and lanthanide series components are present in the compositein an oxidation state above that of the correspondng elemental metal,and substantially all of the alkali or alkaline earth component ispresent in an oxidation state above that of the elemental metal.

Another embodiment is a sulfided nonacidic catalytic compositecomprising a combination of the nonacidic catalytic composite defined inthe fourth embodiment with a sulfiding reagent in an amount sufficientto incorporate about 0.01 to about 1 wt. % sulfur, calculated on anelemental basis.

Yet another embodiment pertains to a method for dehydrogenating adehydrogenatable hydrocarbon which comprises contacting the hydrocarbonwith the nonacidic catalytic composite described in the fourth or fifthembodiment at dehydrogenation conditions including a hydrogen-rich andsubstantially water-free environment.

Other objects and embodiments of the present invention involve specificdetails regarding essential and preferred catalytic ingredients,preferred amounts of ingredients, effective methods or multimetalliccomposite preparation, suitable dehydrogenatable hydrocarbons, operatingconditions for use in the dehydrogenation process, and the likeparticulars. These are hereinafter given in the following detaileddiscussion of each of these facets of the present invention. It is to benoted that (1) the term "nonacidic" means that the catalyst producesless than 10% conversion of 1-butene to isobutylene when tested atdehydrogenation conditions and, preferably, less than % and (2) theexpression "uniformly dispersed throughout a carrier material" isintended to mean that the amount of the subject component, expressed ona weight percent basis, is approximately the same in any reasonablydivisible portion of the carrier material as it is in gross.

Regarding the dehydrogenatable hydrocarbon that is subjected to themethod of the present invention, it can, in general, be an organiccompound having 2 to 30 carbon atoms per molecule and containing atleast one pair of adjacent carbon atoms having hydrogen attachedthereto. That is, it is intended to include within the scope of thepresent invention, the dehydrogenation of any organic compound capableof being dehydrogenated to produce products containing the same numberof carbon atoms but fewer hydrogen atoms, and capable of being vaporizedat the dehydrogenation temperatures used hereon. More particularly,suitable dehydrogenatable hydrocarbons are: aliphatic compoundscontaining 2 to 30 carbon atoms per molecule, alkylaromatic hydrocarbonswhere the alkyl group contains 2 to 6 carbon atoms, and naphthenes oralkyl-substituted naphthenes. Specific examples of suitabledehydrogenatable hydrocarbons are: (1) alkanes such as ethanes, propane,n-butane, isobutane, n-pentane, isopentane, n-hexane, 2-methylpentane,3-methylpentane, 2,2-dimethylbutane, n-heptane, 2-methylhexane,2,2,3-trimethylbutane, and the like compounds; (2) naphthenes such ascyclopentane, cyclohexane, methylcyclopentane, ethylcyclopentane,n-propylcyclopentane, 1,3-dimethylcyclohexane, and the like compounds;and (3) alkylaromatics such as ethylbenzene, n-butylbenzene,1,3,5-triethylbenzene, isopropylbenzene, isobutylbenzene,ethylnaphthalene, and the like compounds.

In a preferred embodiment, the dehydrogenatable hydrocarbon is a normalparaffin hydrocarbon having about 4 to 30 carbon atoms per molecule. Forexample, normal paraffin hydrocarbons containing about 10 to 18 carbonatoms per molecule are dehydrogenated by the subject method to producethe corresponding normal mono-olefin which can, in turn, be alkylatedwith benzene and then sulfonated to make alkylbenzene sulfonatedetergents having superior biodegradability. Likewise, n-alkanes having10 to 18 carbon atoms per molecule can be dehydrogenated to thecorresponding normal mono-olefin which, in turn, can be sulfonated orsulfated to make excellent detergents. Similarly, n-alkanes having 6 to10 carbon atoms can be dehydrogenated to form the correspondingmono-olefin which can, in turn, be hydrated to produce valuablealcohols. Preferred feed streams for the manufacture of detergentintermediates contain a mixture of 4 or 5 adjacent normal paraffinhomologues such as C₁₀ to C₁₃, C₁₁ to C₁₄, C₁₁ to C₁₅ and the likemixtures.

The multimetallic catalyst used in the present invention comprises aporous carrier material or support having combined therewith a uniformdispersion of catalytically effective amounts of a platinum groupcomponent, a Group IVA metallic component, a lanthanide seriescomponent, and in preferred cases, an alkali or alkaline earth componentand/or a sulfur component.

Considering first the porous carrier material utilized in the presentinvention, it is preferred that the material be a porous, adsorptive,high-surface area support having a surface area of about 25 to about 500m² /g. The porous carrier material should be relatively refractory tothe conditions utilized in the dehydrogenation process, and it isintended to include within the scope of the present invention carriermaterials which have traditionally been utilized in dual-functionhydrocarbon conversion catalysts, such as: (1) activated carbon, coke,charcoal; (2) silica or silica gel, silicon carbide, clays, andsilicates including those synthetically prepared and naturallyoccurring, which may or may not be acid treated, for example, attapulgusclay, china clay, diatomaceous earth, fuller's earth, kaolin,kieselguhr, etc.; (3) ceramics, porcelain, crushed firebrick, bauxite;(4) refractory inorganic oxides such as alumina, titanium dioxide,zirconium dioxide, chromium oxide, zinc oxide, magnesia, thoria, boria,silica-alumina, silica-magnesia, chromia-alumina, alumina-boria,silica-zirconia, etc.; (5) crystalline zeolitic aluminosilicates such asnaturally occurring or synthetically prepared mordenite and/orfaujasite, either in the hydrogen form or in a form which has beentreated with multivalent cations; (6) spinels such as MgAl₂ O₄, FeAl₂O₄, ZnAl₂ O₄, MnAl₂ O₄, CaAl₂ O₄ and other like compounds having theformula MO.Al₂ O₃ where M is a metal having a valence of 2; and (7)combinations of elements from one or more of these groups. The preferredporous carrier material for use in the present invention are refractoryinorganic oxides, with best results obtained with an alumina carriermaterial. Suitable alumina materials are the crystalline aluminas knownas the gamma-, eta-, and theta-alumina, with gamma- or eta-aluminagiving best results. In addition, in some embodiments the aluminacarrier material may contain minor proportions of other well-knownrefractory inorganic oxides such as silica, zirconia, magnesia, etc.;however, the preferred support is substantially pure gamma- oreta-alumina. Preferred carrier materials have an apparent bulk densityof about 0.2 to about 0.7 g/cc and surface area characteristics suchthat the average pore diameter is about 20 to about 30 Angstroms, thepore volume is about 0.1 to about 1 cc/g and the surface area is about100 to about 500 m² /g. In general, best results are typically obtainedwith a gamma-alumina carrier material which is used in the form ofspherical particles having: a relatively small diameter (i.e. typicallyabout 1/16 inch), an apparent bulk density of about 0.2 to about 0.6(most preferably about 0.3) g/cc, a pore volume of about 0.4 cc/g, and asurface area of about 150 to about 200 m² /g.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or natural occurring. Whatevertype of alumina is employed, it may be activated prior to use by one ormore treatments including drying, calcination, steaming, etc., and itmay be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide to a salt of aluminum such as aluminum chloride,aluminum nitrate, etc., in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina. The aluminacarrier may be formed in any desired shape such as spheres, pills,cakes, extrudates, powders, granules, etc., and utilized in any desiredsize. For the purpose of the present invention, a particularly preferredform of alumina is the sphere; and alumina spheres may be continuouslymanufactured by the well-known oil drop method which comprises: formingan alumina hydrosol by any of the techniques taught in the art andpreferably by reacting aluminum metal with hydrochloric acid, combiningthe resulting hydrosol with a suitable gelling agent and dropping theresultant mixture into an oil bath maintained at elevated temperatures.The droplets of the mixture remain in the oil bath until they set andform hydrogel spheres. The spheres are then continuously withdrawn fromthe oil bath and typically subjected to specific aging treatments in oiland an ammoniacal solution to further improve their physicalcharacteristics. The resulting aged and gelled particles are then washedand dried at a relatively low temperature of about 300° F. to about 400°F. and subjected to a calcination procedure at a temperature of about850° F. to about 1300° F. for a period of about 1 to about 20 hours. Itis a good practice to subject the calcined particles to a hightemperature treatment with steam in order to remove undesired acidiccomponents such as residual chloride. This procedure effects conversionof the alumina hydrogel to the corresponding crystalline gamma-alumina.See the teachings of U.S. Pat. No. 2,620,314 for additional details.

One essential constituent of the instant multimetallic catalyticcomposite is a Group IVA metallic component. By the use of the genericterm "Group IVA metallic component" it is intended to cover the metalsof Group IVA of the Periodic Table. More specifically, it is intended tocover: germanium, tin, lead and mixtures of these metals. It is anessential feature of the present invention that substantially all of theGroup IVA metallic component is present in the final catalyst in anoxidation state above that of the elemental metal. In other words, thiscomponent may be present in chemical combination with one or more of theother ingredients of the composite, or as a chemical compound of theGroup IVA metal such as the oxide, sulfide, halide, oxyhalide,oxychloride, aluminate, and the like compounds. Based on the evidencecurrently available, it is believed that best results are obtained whensubstantially all of the Group IVA metallic component exists in thefinal composite in the form of the corresponding oxide such as the tinoxide, germanium oxide, and lead oxide, and the subsequently describedoxidation and reduction steps, that are preferably used in thepreparation of the instant composite, are believed to result in acatalytic composite which contains an oxide of the Group IVA metalliccomponent. Regardless of the state in which this component exists in thecomposite, it can be utilized therein in any amount which iscatalytically effective, with the preferred amount being about 0.01 toabout 5 wt. % thereof, calculated on an elemental basis and the mostpreferred amount being about 0.05 to about 2 wt. %. The exact amountselected within this broad range is preferably determined as a functionof the particular Group IVA metal that is utilized. For instance, in thecase where this component is lead, it is preferred to select the amountof this component from the low end of this range--namely, about 0.01 toabout 1 wt. %. Additionally, it is preferred to select the amount oflead as a function of the amount of the platinum group component asexplained hereinafter. In the case where this component is tin, it ispreferred to select from a relatively broader range of about 0.05 toabout 2 wt. % thereof. And, in the preferred case, where this componentis germanium the selection can be made from the full breadth of thestated range--specifically, about 0.01 to about 5 wt. %, with bestresults at about 0.05 to about 2 wt. %.

This Group IVA component may be incorporated in the composite in anysuitable manner known to the art to result in a uniform dispersion ofthe Group IVA moiety throughout the carrier material such as,coprecipitation or cogellation with the porous carrier material, ionexchange with the carrier material, or impregnation of the carriermaterial at any stage in its preparation. It is to be noted that it isintended to include within the scope of the present invention allconventional procedures for incorporating a metallic component in acatalytic composite, and the particular method of incorporation used isnot deemed to be an essential feature of the present invention so longas the Group IVA component is uniformly distributed throughout theporous carrier material. One acceptable method of incorporating theGroup IVA component into the catalytic composite involves cogelling theGroup IVA component during the preparation of the preferred carriermaterial, alumina. This method typically involves the addition of asuitable soluble compound of the Group IVA metal of interest to thealumina hydrosol. The resulting mixture is then commingled with asuitable gelling agent, such as a relatively weak alkaline reagent, andthe resulting mixture is thereafter preferably gelled by dropping into ahot oil bath as explained hereinbefore. After aging, drying andcalcining the resulting particles there is obtained an intimatecombination of the oxide of the Group IVA metal and alumina. Onepreferred method of incorporating this component into the compositeinvolves utilization of a soluble decomposable compound of theparticular Group IVA metal of interest to impregnate the porous carriermaterial either before, during or after the carrier material iscalcined. In general, the solvent used during this impregnation step isselected on the basis of its capability to dissolve the desired GroupIVA compound without affecting the porous carrier material which is tobe impregnated; ordinarily, good results are obtained when water is thesolvent; thus the preferred Group IVA compounds for use in thisimpregnation step are typically water-soluble and decomposable. Examplesof suitable Group IVA compounds are: germanium difluoride, germaniumtetraalkoxide, germanium dioxide, germanium tetrafluoride, germaniummonosulfide, tin chloride, tin bromide, tin dibromide di-iodide, tindichloride di-iodide, tin chromate, tin difluoride, tin tetrafluoride,tin tetraiodide, tin sulfate, tin tartrate, lead acetate, lead bromate,lead bromide, lead chlorate, lead chloride, lead citrate, lead formate,lead lactate, lead malate, lead nitrate, lead nitrite, lead dithionate,and the like compounds. In the case where the Group IVA component isgermanium, a preferred impregnation solution is germanium tetrachloridedissolved in anhydrous alcohol. In the case of tin, tin chloridedissolved in water is preferred. In the case of lead, lead nitratedissolved in water is preferred. Regardless of which impregnationsolution is utilized, the Group IVA component can be impregnated eitherprior to, simultaneously with, or after the other metallic componentsare added to the carrier material. Ordinarily, best results are obtainedwhen this component is impregnated simultaneously with the othermetallic components of the composite. Likewise, best results areordinarily obtained when the Group IVA component is germanium oxide ortin oxide.

Regardless of which Group IVA compound is used in the preferredimpregnation step, it is essential that the Group IVA metallic componentbe uniformly distributed throughout the carrier material. In order toachieve this objective when this component in incorporated byimpregnation, it is necessary to maintain the pH of the impregnationsolution at a relatively low level corresponding to about 7 to about 1or less and to dilute the impregnation solution to a volume which is atleast approximately the same or greater than the volume of the carriermaterial which is impregnated. It is preferred to use a volume ratio ofimpregnation solution to carrier material of at least 1:1 and preferablyabout 2:1 to about 10:1 or more. Similarly, it is preferred to use arelatively long contact time during the impregnation step ranging fromabout 1/4 hour up to about 1/2 hour or more before trying to removeexcess solvent in order to insure a high dispersion of the Group IVAmetallic component in the carrier material. The carrier material is,likewise, preferably constantly agitated during this preferredimpregnation step.

A second essential ingredient of the subject catalyst is the platinumgroup component. That is, it is intended to cover the use of platinum orpalladium or iridium or rhodium or osmium or ruthenium or mixturesthereof as a second component of the present composite. It is anessential feature of the present invention that substantially all of theplatinum group component exists within the final catalytic composite inthe elemental metallic state (i.e. as elemental platinum or palladium oriridium etc.). Generally the amount of the second component used in thefinal composite is relatively small compared to the amount of the othercomponents combined therewith. In fact, the platinum group componentgenerally will comprise about 0.01 to about 2 wt. % of the finalcatalytic composite, calculated on an elemental basis. Excellent resultsare obtained when the catalyst contains about 0.05 to about 1 wt. % ofplatinum, iridium, rhodium or palladium metal.

This platinum group component may be incorporated in the catalyticcomposite in any suitable manner known to result in a relatively uniformdistribution of this component in the carrier material such ascoprecipitation or cogellation, ion-exchange, or impregnation. Thepreferred method of preparing the catalyst involves the utilization of asoluble, decomposable compound of a platinum group metal to impregnatethe carrier material in a relatively uniform manner. For example, thiscomponent may be added to the support by commingling the latter with anaqueous solution of chloroplatinic, chloroiridic or chloropalladic acid.Other water-soluble compounds of platinum group metals may be employedin impregnation solutions and include ammonium chloroplatinate,bromoplatinic acid, platinum dichloride, platinum tetrachloride hydrate,platinum dichlorocarbonyl dichloride, dinitrodiaminoplatinum, tetramineplatinum chloride, palladium chloride, palladium nitrate, palladiumsulfate, rhodium nitrate, rhodium trichloride hydrate, etc. Theutilization of a platinum group metal chloride compound, such aschloroplatinic, chloroiridic or chloropalladic acid, is preferred.Hydrogen chloride, nitric acid or the like acid is also generally addedto the impregnation solution in order to facilitate the uniformdistribution of the metallic component throughout the carrier material.In addition, it is generally preferred to impregnate the carriermaterial after it has been calcined in order to minimize the risk ofwashing away the valuable platinum or palladium compounds; however, insome cases it may be advantageous to impregnate the carrier materialwhen it is in a gelled state.

Yet another essential ingredient of the present catalytic composite is alanthanide series component. By the use of the generic expression"lanthanide series component" it is intended to cover the 15 elementsand mixtures thereof that are commonly known as the "lanthanide seriesmetals" or "rare earths metals". Specifically, included within thisdefinition are the following elements: lanthanum, cerium, praseodymium,neodymium, promethium, samarium, europium, gadolinium, terbium,dysprosium, holmium, erbium, thulium, ytterbium and lutetium. Thiscomponent may be present in the instant multimetallic composite in anyform wherein substantially all of the lanthanide series element ispresent in an oxidation state above that of the corresponding metal suchas in chemical combination with one or more of the other ingredients ofthe composite, or as a chemical compound such as a lanthanide seriesoxide, sulfide, halide, oxychloride, aluminate, and the like. However,best results are believed to be obtained when substantially all of thelanthanide series component exists in the form of the correspondingoxide and the subsequently described oxidation and prereductionprocedure is believed, on the basis of the available evidence, to resultin this condition. This lanthanide series component may be utilized inthe composite in any amount which is catalytically effective, with thepreferred amount being about 0.01 to about 1 wt. % thereof, calculatedon an elemental lanthanide series metal basis. Typically best resultsare obtained with about 0.05 to about 0.5 wt. % lanthanide serieselement. According to the present invention, it is essential to selectthe specific amount of lanthanide series metal from within this broadweight range as a function of the amount of the platinum groupcomponent, on an atomic basis, as is explained hereinafter. Thelanthanide series elements that are especially preferred for purposes ofthe present invention are lanthanum, cerium, and neodymium, withneodymium giving best results.

The lanthanide series component may be incorporated into the catalyticcomposite in any suitable manner known to those skilled in the catalystformulation art which ultimately results in a uniform dispersion of thelanthanide series moiety in the carrier material. In addition, it may beadded at any stage of the preparation of the composite--either duringpreparation of the carrier material or thereafter--and the precisemethod of incorporation used is not deemed to be critical. However, bestresults are obtained when the lanthanide series component isincorporated in a manner such that it is relatively uniformlydistributed throughout the carrier material in a positive oxidationstate or a state which is easily converted to a positive oxidation statein the subsequently described oxidation step. One preferred procedurefor incorporating this component into the composite involves cogellingor coprecipitating the lanthanide component during the preparation ofthe preferred carrier material, alumina. This procedure usuallycomprehends the addition of a soluble, decomposable compound of alanthanide series element such as neodymium nitrate to the aluminahydrosol before it is gelled. The resulting mixture is then finished byconventional gelling, aging, drying and calcination steps as explainedhereinbefore. Another preferred way of incorporating this component isan impregnation step wherein the porous carrier material is impregnatedwith a suitable lanthanide series compound-containing solution eitherbefore, during or after the carrier material is calcined. Preferredimpregnation solutions are aqueous solutions of water-soluble,decomposable lanthanide series compounds such as a lanthanide acetate,lanthanide bromide, a lanthanide perchlorate, a lanthanide chloride, alanthanide iodide, a lanthanide nitrate, and the like compounds. Bestresults are ordinarily obtained when the impregnation solution is anaqueous solution of a lanthanide chloride or a lanthanide nitrate. Thislanthanide series component can be added to the carrier material, eitherprior to, simultaneously with, or after the other metallic componentsare combined therewith. Best results are usually achieved when thiscomponent is added simultaneously with the platinum group component. Infact, excellent results are obtained, as reported in the examples, witha impregnation procedure using a tin-containing alumina carrier materialand an aqueous impregnation solution comprising the desired amounts ofchloroplatinic acid, a lanthanide nitrate, and nitric acid.

A highly preferred ingredient of the catalyst used in the presentinvention is the alkali or alkaline earth component. More specifically,this component is selected from the group consisting of the compounds ofthe alkali metals-- cesium, rubidium, potassium, sodium, and lithium--and of the alkaline earth metals-- calcium, strontium, barium, andmagnesium. This component exists within the catalytic composite in anoxidation state above that of the elemental metal such as a relativelystable compound such as the oxide or hydroxide, or in combination withone or more of the other components of the composite, or in combinationwith the carrier material such as, for example, in the form of an alkalior alkaline earth metal aluminate. Since as is explained hereinafter,the composite containing the alkali or alkaline earth component isalways calcined or oxidized in an air atmosphere before use in thedehydrogenation of hydrocarbons, the most likely state this componentexists in during use in the dehydrogenation reaction is thecorresponding metallic oxide such as lithium oxide, potassium oxide,sodium oxide, and the like. Regardless of what precise form in which itexists in the composite, the amount of this component utilized ispreferably selected to provide a nonacidic composite containing about0.1 to about 5 wt. % of the alkali metal or alkaline earth metal, and,more preferably, about 0.25 to about 3.5 wt. %, Best results areobtained when this component is a compound of lithium or potassium. Thefunction of this component is to neutralize any of the acidic materialsuch as halogen which may have been used in the preparation of thepresent catalyst so that the final catalyst is nonacidic.

This alkali or alkaline earth component may be combined with the porouscarrier material in any manner known to those skilled in the art toresult in a relatively uniform dispersion of this component throughoutthe carrier material with consequential neutralization of any acidicsites which may be present therein. Typically good results are obtainedwhen it is combined by impregnation, coprecipitation, ion-exchange, andthe like procedures. The preferred procedure, however, involvesimpregnation of the carrier material either before, during, or after itis calcined, or before, during, or after the other metallic ingredientsare added to the carrier material. Best results are ordinarily obtainedwhen this component is added to the carrier material after the platinumgroup, Group IVA metallic and lanthanide series components because thealkali metal or alkaline earth metal component acts to neutralize theacidic materials used in the preferred impregnation procedure for thesemetallic components. In fact, it is preferred to add the other metalliccomponents to the carrier material, oxidize the resulting composite in awet air stream at a high temperature (i.e. typically about 600° to 1000°F.), then treat the resulting oxidized composite with steam or a mixtureof air and steam at a relatively high temperature of about 800° to about1050° F. in order to remove at least a portion of any residual acidityand thereafter add the alkali metal or alkaline earth component.Typically, the impregnation of the carrier material with this componentis performed by contacting the carrier material with a solution of asuitable decomposable compound or salt of the desired alkali or alkalineearth metal. Hence, suitable compounds include the alkali metal oralkaline earth metal halides, sulfates, nitrates, acetates, carbonates,phosphates, and the like compounds. For example, excellent results areobtained by impregnating the carrier material after the other metalliccomponents have been combined therewith, with an aqueous solution oflithium nitrate or potassium nitrate.

Regarding the preferred amounts of the various metallic components ofthe subject catalyst, I have found it to be an essential practice tospecify the amounts of the lanthanide series component as a function ofthe amount of the platinum group component. On this basis, the amount ofthe lanthanide series component is selected so that the atomic ratio oflanthanide series metal to the platinum group metal contained in thecomposite is about 0.1:1 to 1.25:1, with best results obtained when therange is about 0.4:1 to about 1:1. Similarly, it is a preferred practiceto select the amount of the Group IVA metallic component to produce acomposite containing an atomic ratio of Group IVA metal to platinumgroup metal within the broad range of about 0.05:1 to 10:1. However, forthe Group IVA metal to platinum group metal ratio, the best practice isto select this ratio on the basis of the following preferred ranges forthe individual Group IVA species: (1) for germanium, it is about 0.3:1to 10:1, with the most preferred range being about 0.6:1 to about 6:1;(2) for tin, it is about 0.1:1 to 3:1, with the most preferred rangebeing about 0.5:1 to 1.5:1; and, (3) for lead, it is about 0.05:1 to0.9:1, with the most preferred range being about 0.1:1 to 0.75:1. In thesame manner, the amount of the alkali or alkaline earth component isordinarily selected to produce a composite having an atomic ratio ofalkali metal or alkaline earth metal to platinum group metal of about5:1 to about 100:1 or more, with the preferred range being about 10:1 toabout 75:1.

Another significant parameter for the instant nonacidic catalyst is the"total metals content" which is defined to be the sum of the platinumgroup component, the Group IVA metallic component, the lanthanide seriescomponent and the alkali or alkaline earth component, calculated on anelemental metal basis. Good results are ordinarily obtained with thesubject catalyst when this parameter is fixed at a value of about 0.15to about 3.5 wt. %, with best results ordinarily achieved at a metalsloading of about 0.3 to about 3 wt. %.

Integrating the above discussion of each of the essential and preferredcomponents of the catalytic composite used in the present invention, itis evident that an especially preferred nonacidic catalytic compositecomprises a combination of a platinum group component, a Group IVAmetallic component, a lanthanide series component, and an alkali oralkaline earth component with an alumina carrier material in amountssufficient to result in the composite containing, on an elemental basis,from about 0.05 to about 1 wt. % platinum group metal, about 0.05 toabout 2 wt. % Group IVA metal, about 0.25 to about 3.5 wt. % of thealkali metal or alkaline earth metal, and an atomic ratio of lanthanideseries metal to platinum group metal of about 0.4:1 to about 1:1.

Regardless of the details of how the components of the catalyst arecombined with the porous carrier material, the resulting multimetalliccomposite generally will be dried at a temperature of about 200° F. toabout 600° F. for a period of from about 2 to about 24 hours or more,and finally calcined or oxidixed at a temperature of about 600° F. toabout 1100° F. in an air atmosphere for a period of about 0.5 to 10hours, preferably about 1 to about 5 hours, in order to convertsubstantially all the metallic components to the corresponding oxideform. When acidic components are present in any of the reagents used toeffect incorporation of any one of the components of the subjectcomposite, it is a good practice to subject the resulting composite to ahigh temperature treatment with steam or with a mixture of steam andair, either before, during or after this oxidation step in order toremove as much as possible of the undesired acidic components. Forexample, when the platinum or palladium component is incorporated byimpregnating the carrier material with chloroplatinic or chloropalladicacid, it is preferred to subject the resulting composite to a hightemperature treatment with steam or a mixture of steam and air at atemperature of about 600° to 1100° F. in order to remove as much aspossible of the undesired chloride.

The resultant oxidized catalytic composite is subjected to asubstantially water-free reduction step prior to its use in thedehydrogenation of hydrocarbons. This step is designed to selectivelyreduce the platinum group component to the elemental metallic state andto insure a uniform and finely divided dispersion of the metalliccomponents throughout the carrier material, while maintaining the GroupIVA metallic, lanthanide series, and alkali or alkaline earth componentsin a positive oxidation state. It is a good practice to dry the oxidizedcatalyst prior to this reduction step by passing a stream of dry air ornitrogen through same at a temperature of about 500° to 1100° F. and aGHSV of about 100 to 800 hr.⁻¹ until the effluent stream contains lessthan 1000 ppm. of H₂ O and preferably less than 500 ppm. Preferably, asubstantially pure and dry hydrogen stream (i.e. less than 20 vol. ppm.H₂ O) is used as the reducing agent in this reduction step. The reducingagent is contacted with the oxidized catalyst at conditions including atemperature of about 400° F. to about 1200° F., a GHSV of about 300 to1000 hr.⁻¹, and a period of time of about 0.5 to 10 hours at leasteffective to bring about the desired selective reduction of the metallicingredients. This reduction treatment may be performed in situ as partof a start-up sequence if precautions are taken to predry the plant to asubstantially water-free state and if a substantially water-freehydrogen stream is used.

The resulting selectively reduced catalytic composite may in mostcircumstances associated with hydrocarbon dehydrogenation service bebeneficially subjected to a presulfiding operation designed toincorporate in the catalytic composite from about 0.01 to about 1 wt. %sulfur, and preferably about 0.05 to about 0.5 wt. % sulfur, calculatedon an elemental basis. Preferably, this presulfiding treatment takesplace in the presence of hydrogen and a suitable sulfur-containingsulfiding reagent such as hydrogen sulfide, lower molecular weightmercaptans, organic sulfides and disulfides, etc. Typically, thisprocedure comprises treating the selectively reduced catalyst with asulfiding reagent such as a mixture of hydrogen and hydrogen sulfidehaving about 10 moles of hydrogen per mole of hydrogen sulfide atconditions sufficient to effect the desired incorporation of sulfur,generally including a temperature ranging from about 50° F. up to about1100° F. or more. It is generally a good practice to perform thispresulfiding step under substantially water-free conditions. It iswithin the scope of the present invention to maintain or achieve thesulfided state of the instant catalyst during use in the dehydrogenationof hydrocarbons by continuously or periodically adding a decomposablesulfur-containing compound, such as the sulfiding reagents previouslymentioned, to the reactor containing the catalyst in an amountsufficient to provide about 1 to 500 wt. ppm., preferably 1 to 20 wt.ppm. of sulfur based on hydrocarbon charge.

According to the method of the present invention, the dehydrogenatablehydrocarbon is contacted with the multimetallic catalytic compositedescribed above in a dehydrogenation zone maintained at dehydrogenationconditions including a hydrogen-rich and substantially water-freeenvironment. This contacting may be accomplished by using the catalystin a fixed bed system, a moving bed system, a fluidized bed system, orin a batch type operation; however, in view of the danger of attritionlosses of the valuable catalyst and of well-known operationaladvantages, it is preferred to use a fixed bed system. In this system,the hydrocarbon feed stream is preheated by any suitable heating meansto the desired reaction temperature and then passed into adehydrogenation zone containing a fixed bed of the catalyst previouslycharacterized. It is, of course, understood that the dehydrogenationzone may be one or more separate reactors with suitable heating meanstherebetween to insure that the desired conversion temperature ismaintained at the entrance to each reactor. It is also to be noted thatthe reactants may be contacted with the catalyst bed in either upward,downward, or radial flow fashion with the latter being preferred. Inaddition, it is to be noted that the reactants may be in the liquidphase, a mixed liquid-vapor phase, or a vapor phase when they contactthe catalyst, with best results obtained in the vapor phase.

A feature of the present dehydrogenation method is that it is performedin a reaction environment which is maintained in a hydrogen-richcondition and in a condition such that it is substantially free of majoramounts of water i.e., steam at the dehydrogenation condition used). Ahydrogen-rich reaction environment is preferred because it serves thefunctions of not only lowering the partial pressure of thedehydrogenatable hydrocarbon, but also of suppressing the formation ofhydrogen-deficient, carbonaceous deposits on the catalytic composite andof maintaining the platinum group component of the catalyst in theelemental metallic state. Ordinarily, hydrogen is utilized in amountssufficient to insure a hydrogen to hydrocarbon mole ratio of about 1:1to about 20:1, with best results obtained in the range of about 1.5:1 toabout 10:1. The hydrogen stream charged to the dehydrogenation zone willtypically be recycled hydrogen obtained from the effluent stream fromthis zone after a suitable hydrogen separation step. The expression"substantially water-free environment" as used herein means that thecatalyst environment in the reaction zone is maintained free of grossamounts of water; more specifically, the total amount of water orwater-producing substances entering the zone is maintained at a valuecorresponding to less than 5,000 wt. ppm. of the total amount ofhydrocarbon charged to this zone. On a percentage of feed hydrocarbonbasis, this means that the amount of water in the reaction environmentis held at a level less than 0.5% of the weight of hydrocarbon charged.In the case where the reaction environment is bone dry due to theabsence of any water in the feed or hydrogen stream passed to thereaction zone, it is a preferred practice to add water or awater-producing substance (such as an alcohol, ketone, ether, aldehyde,or the like oxygen-containing decomposable organic compound) to thedehydrogenation zone in an amount calculated on the basis of equivalentwater, corresponding to about 50 to less than about 5,000 wt. ppm. ofthe hydrocarbon charge stock, with about 1000 to 2,500 wt. ppm. of watergiving best results.

Regarding the conditions utilized in the process of the presentinvention, these are generally selected from the dehydrogenationconditions well known to those skilled in the art for the particulardehydrogenatable hydrocarbon which is charged to the process. Morespecifically, suitable conversion temperatures are selected from therange of about 700° to about 1200° F. with a value being selected fromthe lower portion of this range for the more easily dehydrogenatedhydrocarbons such as the long chain normal paraffins and from the higherportion of this range for the more difficultly dehydrogenatedhydrocarbons such as propane, butane, and the like hydrocarbons. Forexample, for the dehydrogenation of C₆ to C₃₀ normal paraffins, bestresults are ordinarily obtained at a temperature of about 800° to about950° F. The pressure utilized is ordinarily selected at a value which isas low as possible consistent with the maintenance of catalyst stabilityand is usually about 0.1 to about 10 atmospheres with best resultsordinarily obtained in the range of about 0.5 to about 3 atmospheres. Inaddition, a liquid velocity space valocity (calculated on the basis ofthe volume amount, as a liquid, of hydrocarbon charged to thedehydrogenation zone per hour divided by the volume of the catalyst bedutilized) is selected from the range of about 1 to about 40 hr.⁻¹, withbest results for the dehydrogenation of long chain normal paraffinstypically obtained at a relatively high space velocity of about 25 to 35hr.⁻¹.

Regardless of the details concerning the operation of thedehydrogenation step, an effluent stream will be withdrawn therefrom.This effluent will usually contain unconverted dehydrogenatablehydrocarbons, hydrogen, and products of the dehydrogenation reaction.This stream is typically cooled and passed to a hydrogen-separating zonewherein a hydrogen-rich vapor phase is allowed to separate from ahydrocarbon-rich liquid phase. In general, it is usually desired torecover the unreacted dehydrogenatable hydrocarbon from thishydrocarbon-rich liquid phase in order to make the dehydrogenationprocess economically attractive. This recovery operation can beaccomplished in any suitable manner known to the art such as by passingthe hydrocarbon-rich liquid phase through a bed of suitable adsorbentmaterial which has the capability to selectively retain thedehydrogenated hydrocarbons contained therein or by contacting same witha solvent having a high selectivity for the dehydrogenated hydrocarbon,or by a suitable fractionation scheme where feasible. In the case wherethe dehydrogenated hydrocarbon is a mono-olefin, suitable adsorbentshaving this capacility are activated silica gel, activated carbon,activated alumina, various types of specially prepared zeoliticcrystalline aluminosilicates, molecular sieves, and the like adsorbents.In another typical case, the dehydrogenated hydrocarbons can beseparated from the unconverted dehydrogenatable hydrocarbons byutilizing the inherent capability of the dehydrogenated hydrocarbons toeasily enter into several well-known chemical reactions such asalkylation, oligomerization, halogenation, sulfonation, hydration,oxidation, and the like reactions. Irrespective of how thedehydrogenated hydrocarbons are separated from the unreactedhydrocarbons, a stream containing the unreacted dehydrogenatablehydrocarbons will typically be recovered from this hydrocarbonseparation step and recycled to the dehydrogenation step. Likewise, thehydrogen phase present in the hydrogen-separating zone will be withdrawntherefrom, a portion of it vented from the system in order to remove thenet hydrogen make, and the remaining portion is typically recycledthrough suitable compressing means to the dehydrogenation step in orderto provide diluent hydrogen therefor.

In a preferred embodiment of the present invention wherein long chainnormal paraffin hydrocarbons are dehydrogenated to the correspondingnomal mono-olefins, a preferred mode of operation of this hydrocarbonrecovery step involves an alkylation reaction. In this mode, thehydrocarbon-rich liquid phase withdrawn from the hydrogen-separatingzone is combined with a stream containing an alkylatable aromatic andthe resulting mixture passed to an alkylation zone containing a suitablehighly acid catalyst such as an anhydrous solution of hydrogen fluoride.In the alkylation zone the mono-olefins react with alkylatable aromaticwhile the unconverted normal paraffins remain substantially unchanged.The effluent stream from the alkylation zone can then be easilyseparated, typically by means of a suitable fractionation system, toallow recovery of the unreacted normal paraffins. The resulting streamof unconverted normal paraffins is then usually recycled to thedehydrogenation step of the present invention.

The following working examples are introduced to illustrate further thedehydrogenation method and nonacidic multimetallic catalytic compositeof the present invention. These examples of specific embodiments of thepresent invention are intended to be illustrative rather thenrestrictive.

These examples are all performed in a laboratory scale dehydrogenationplant comprising a reactor, a hydrogen separating zone, heating means,cooling means, pumping means, compressing means, and the likeconventional equipment. In this plant, a substantially water-free feedstream containing the dehydrogenatable hydrocarbon is combined with ahydrogen stream containing water in an amount corresponding to about2000 wt. ppm. of the hydrocarboon feed and the resultant mixture heatedto the desired conversion temperature, which refers herein to thetemperature maintained at the inlet to the reactor. The heated mixtureis then passed into contact with the instant multimetallic catalystwhich is maintained in a hydrogen-rich and substantially water-freeenvironment as a fixed bed of catalyst particles in the reactor. Thepressures reported herein are recorded at the outlet from the reactor.An effluent stream is withdrawn from the reactor, cooled, and passedinto the hydrogen-separating zone wherein a hydrogen-rich gas phaseseparates from a hydrocarbon-rich liquid phase containing dehydrogenatedhydrocarbons, unconverted dehydrogenatable hydrocarbons, and a minoramount of side products of the dehydrogenation reaction. A portion ofthe hydrogen-rich gas phase is recovered as excess recycle gas with theremaining portion being continuously recycled, after water addition asneeded, through suitable compressing means to the heating zone asdescribed above. The hydrocarbon-rich liquid phase from the separatingzone is withdrawn therefrom and subjected to analysis to determineconversion and selectivity for the desired dehydrogenated hydrocarbon aswill be indicated in the examples. Conversion numbers of thedehydrogenatable hydrocarbon reported herein are all calculated on thebasis of disappearance of the dehydrogenatable hydrocarbon and areexpressed in mole percent. Similarly, selectivity numbers are reportedon the basis of moles of desired hydrocarbon produced per 100 moles ofdehydrogenatable hydrocarbon converted.

All of the catalysts utilized in these examples are prepared accordingto the following preferred method with suitable modification instoichiometry to achieve the compositions reported in each example.First, a tin-containing alumina carrier material comprising 1/16 inchspheres having an apparent bulk density of about 0.3 g/cc is preparedby: forming an aluminum hydroxy chloride sol by dissolving substantiallypure aluminum pellets in a hydrochloric acid solution, adding stannicchloride and hexamethylenetetramine to the resulting alumina sol,gelling the resulting solution by dropping it into an oil bath to formspherical particles of a tin-containing alumina hydrogel, aging, andwashing the resulting particles with an ammoniacal solution and finallydrying, calcining and steaming the aged and washed particles to formspherical particles of gamma-alumina containing a uniform dispersion ofthe desired quantity of tin in the form of tin oxide and substantiallyless than 0.1 wt. % combined chloride. Additional details as to thismethod of preparing this alumina carrier material are given in theteachings of U.S. Pat. No. 2,620,314.

The resulting gamma-alumina particles are then contacted at suitableimpregnation conditions with an aqueous impregnation solution containingchloroplatinic acid, neodymium nitrate and nitric acid in amountssufficient to yield a final multimetallic catalytic composite containinga uniform dispersion of the hereinafter specified amounts of platinumand neodymium. The nitric acid is utilized in this impregnation solutionin an amount of about 5 wt. % of the alumina particles. In order toensure a uniform dispersion of the metallic components in the carriermaterial, the impregnation solution is maintained in contact with thecarrier material particles for about 1/2 hour at a temperature of about70° F. with constant agitation. The impregnated spheres are then driedat a temperature of about 225° F. for about an hour and thereaftercalcined or oxidized in an air atmosphere containing about 5 to 25 vol.% H₂ O at a temperature of about 500° F. to about 1000° F. for about 2to 10 hours effective to convert all of the metallic components to thecorresponding oxide forms. In general, it is a good practice tothereafter treat the resulting oxidized particles with an air streamcontaining about 10 to about 30% steam at a temperature of about 800° F.to about 1000° F. for an additional period of about 1 to about 5 hoursin order to reduce any residual combined chloride contained in thecatalyst to a value of less than 0.5 wt. % and preferably less than 0.2wt. %.

In the cases shown in the examples where the catalyst utilized containsan alkali or alkaline earth component, this component is also added tothe oxidized and stem-treated multimetallic catalyst in this secondimpregnation step. This second impregnation step involves contacting theoxidized and steamed multimetallic catalyst with an aqueous solution ofa suitable soluble and decomposable salt of the alkali or alkaline earthcomponent under conditions selected to result in a uniform dispersion ofthis component in the carrier material. For the catalysts utilized inthe present examples, the salts are lithium nitrate or potassiumnitrate. The amounts of the salts of the alkali metal utilized arechosen to result in a final catalyst having the desired nonacidiccharacteristics. The resulting alkali or alkaline earth-impregnatedparticles are then preferably dried, oxidized, and steamed in an airatmosphere in much the same manner as is described above following thefirst impregnation step. In some cases, it is possible to combine bothof these impregnation steps into a single step, thereby significantlyreducing the time and complexity of the catalyst manufacturingprocedure.

The resulting oxidized catalyst is thereafter subjected to a drying stepwhich involves contacting the oxidized particles with a dry air streamat a temperature of about 1050° F., a GHSV of 300 hr.⁻¹ for a period ofabout 10 hours. The dried catalyst is then purged with a dry nitrogenstream and thereafter selectively reduced by contacting with a dryhydrogen stream at conditions including a temperature of about 870° F.,atmospheric pressure and a gas hourly space velocity of about 500 hr.⁻¹,for a period of about 1 to 10 hours effective to reduce substantiallyall of the platinum component to the elemental metallic state, whilemaintaining the neodymium, tin and alkali or alkaline earth componentsin a positive oxidation state.

EXAMPLE I

The reactor is loaded with 100 cc of a catalyst containing, on anelemental basis, 0.47 wt. % platinum, 0.5 wt. % tin, 0.26 wt. %neodymium, and less than 0.15 wt. % chloride. This corresponds to atomicratios of tin to platinum of 1.75:1 and of neodymium to platinum of0.75:1. The feed stream utilized is commercial grade isobutanecontaining 99.7 wt. % isobutane and 0.33 wt. % normal butane. The feedstream is contacted with the catalyst at a temperature of about 1030°F., a pressure of 10 psig., a liquid hourly space velocity of 4.0 hr.⁻¹,and a hydrogen to hydrocarbon mole ratio of 2:1. The dehydrogenationplant is lined-out at these conditions and a 20 hour test periodcommenced. The hydrocarbon product stream from the plant is continuouslyanalyzed by GLC (gas liquid chromatography) and a high conversion ofisobutane is observed with good yields of isobutylene.

EXAMPLE II

The catalyst contains, on an elemental basis, 0.375 wt. % platinum, 0.25wt. % tin, 0.2 wt. % neodymium, 0.6 wt. % lithium, and less than 0.15wt. % combined chloride. The pertinent atomic ratios are: tin toplatinum of 1.1:1, neodymium to platinum of 0.72:1 and lithium toplatinum of 45:1. The feed stream is commercial grade normal dodecane.The dehydrogenation reactor is operated at a temperature of 860° F., apressure of 10 psig, a liquid hourly space velocity of 32 hr.⁻¹, and arecycle gas to hydrocarbon mole ratio of 8:1. After a line-out period, a20 hour test period is performed during which the average conversion ofthe normal dodecane is maintained at a high level with a selectivity fornormal dodecene of about 90%.

EXAMPLE III

The catalyst is the same as utilized in Example II. The feed stream isnormal tetradecane. The conditions utilized are a temperature of 830°F., a pressure of 20 psig., a liquid hourly space velocity of 32 hr.⁻¹,and a recycle gas to hydrocarbon mole ratio of 8:1. After a line-outperiod, a 20 hour test shows an average conversion of about 12%, and aselectivity for normal tetradecene of about 90%.

EXAMPLE IV

The catalyst is the same as utilized in Example I. The feed stream issubstantially pure cyclohexane. The conditions utilized are atemperature of 900° F., a pressure of 100 psig., a liquid hourly spacevelocity of 3.0 hr.⁻¹, and a recycle gas to hydrocarbon mole ratio of4:1. After a line-out period, a 20 hour test is performed with almostquantitative conversion of cyclohexane to benzene and hydrogen.

EXAMPLE V

The catalyst contains, on an elemental basis, 0.6 wt. % platinum, 0.4wt. % tin, 0.25 wt. % neodymium, 1.5 wt. % potassium, and less than 0.2wt. % combined chloride. The important atomic ratios are: tin toplatinum of 1.1:1, neodymium to platinum of 0.56:1 and potassium toplatinum of 12.5:1. The feed stream is commercial grade ethylbenzene.The conditions utilized are a pressure of 15 psig., a liquid hourlyspace velocity of 32 hr.⁻¹, a temperature of 1025° F., and a recycle gasto hydrocarbon mole ratio of 8:1. During a 20 hour test period, 85% ormore of equilibrium conversion of the ethylbenzene is observed. Theselectivity for styrene is about 95%.

It is intended to cover by the following claims, all changes andmodifications of the above disclosure of the present invention whichwould be self-evident to a man of ordinary skill in the catalystformulation art or in the hydrocarbon dehydrogenation art.

I claim as my invention:
 1. A method for dehydrogenating adehydrogenatable hydrocarbon comprising contacting the hydrocarbon, atdehydrogenation conditions including a hydrogen-rich and substantiallywater-free environment, with a catalytic composite of a porous carriermaterial containing, calculated on a wt. % of finished composite and onan elemental basis, about 0.01 to about 2 wt. % platinum group metal,about 0.01 to about 5 wt. % Group IVA metal, and a lanthanide seriescomponent in an amount sufficient to result in an atomic ratio oflanthanide series metal to platinum group metal of about 0.1:1 to about1.25:1; wherein the platinum group metal, Group IVA metal and lanthanideseries component are uniformly dispersed throughout the porous carriermaterial; wherein substantially all of the platinum group metal ispresent in the elemental metallic state; and wherein substantially allof the Group IVA metal and the lanthanide series component are presentin an oxidation state above that of the corresponding elemental metal.2. A method as defined in claim 1 wherein the environment contains lessthan 5,000 wt. ppm. of H₂ O, calculated on the basis of weight ofhydrocarbon charged.
 3. A method as defined in claim 1 wherein theporous carrier material is a refractory inorganic oxide.
 4. A method asdefined in claim 3 wherein the refractory inorganic oxide is alumina. 5.A method as defined in claim 1 wherein the platinum group metal isplatinum.
 6. A method as defined in claim 1 wherein the platinum groupmetal is iridium.
 7. A method as defined in claim 1 wherein the platinumgroup metal is palladium.
 8. A method as defined in claim 1 wherein theplatinum group metal is rhodium.
 9. A method as defined in claim 1wherein the lanthanide series component is neodymium.
 10. A method asdefined in claim 1 wherein the lanthanide series component is cerium.11. A method as defined in claim 1 wherein the lanthanide seriescomponent is lanthanum.
 12. A method as defined in claim 1 wherein theGroup IVA metal is germanium.
 13. A method as defined in claim 1 whereinthe Group IVA metal is lead.
 14. A method as defined in claim 1 whereinthe Group IVA metal is tin.
 15. A method as defined in claim 1 whereinthe dehydrogenatable hydrocarbon is an aliphatic hydrocarbon containing2 to 30 carbon atoms per molecule.
 16. A method as defined in claim 1wherein the dehydrogenatable hydrocarbon is a normal paraffinhydrocarbon containing 4 to 30 carbon atoms per molecule.
 17. A methodas defined in claim 1 wherein the dehydrogenatable hydrocarbon is anaphthene.
 18. A method as defined in claim 1 wherein thedehydrogenatable hydrocarbon is an alkylaromatic, the alkyl group ofwhich contains about 2 to 6 carbon atoms.
 19. A method as defined inclaim 1 wherein the dehydrogenation conditions include a temperature of700° to about 1200° F., a pressure of 0.1 to 10 atmospheres, a LHSV of 1to 40 hr.⁻¹, and a hydrogen to hydrocarbon mole ratio of about 1:1 toabout 20:1.
 20. A method as defined in claim 1 wherein the compositecontains, on an elemental basis, about 0.05 to about 1 wt. % platinumgroup metal, about 0.01 to about 2 wt. % Group IVA metal and an atomicratio of lanthanide series metal to platinum group metal of about 0.4:1to about 1:1.
 21. A method as defined in claim 1 wherein the metalscontent of the catalytic composite is adjusted so that the atomic ratioof Group IVA metal to platinum group metal is about 0.05:1 to about10:1.
 22. A method as defined in claim 1 wherein the catalytic compositeis sulfided in an amount sufficient to incorporate about 0.05 to about0.5 wt. % sulfur, calculated on an elemental basis.
 23. A method asdefined in claim 1 wherein substantially all of the Group IVA metal ispresent in the catalytic composite in the form of the correspondingoxide.
 24. A method as defined in claim 1 wherein substantially all ofthe lanthanide series component is present in the catalytic composite inthe form of the corresponding oxide.
 25. A method for dehydrogenating adehydrogenatable hydrocarbon comprising contacting the hydrocarbon, atdehydrogenation conditions including a hydrogen-rich and substantiallywater-free environment, with a nonacidic catalytic composite consistingessentially of a porous carrier material containing, calculated on a wt.% of finished composite and on an elemental basis, about 0.01 to about 2wt. % platinum group metal, about 0.01 to about 5 wt. % Group IVA metal,about 0.1 to about 5 wt. % alkali metal or alkaline earth metal, and alanthanide series component in an amount sufficient to result in anatomic ratio of lanthanide series metal to platinum group metal of about0.1:1 to about 1.25:1 wherein the platinum group metal, Group IVA metal,lanthanide series component, and alkali metal or alkaline earth metalare uniformly dispersed throughout the porous carrier material; whereinsubstantially all of the platinum group metal is present in theelemental metallic state; wherein substantially all of the alkali metalor alkaline earth metal is present in an oxidation state above that ofthe elemental metal; and wherein substantially all of the Group IVAmetal and the lanthanide series component are present in an oxidationstate above that of the elemental metal.
 26. A method as defined inclaim 25 wherein the porous carrier material is a refractory inorganicoxide.
 27. A method as defined in claim 26 wherein the refractoryinorganic oxide is alumina.
 28. A method as defined in claim 25 whereinthe alkali metal or alkaline earth metal is potassium.
 29. A method asdefined in claim 25 wherein the alkali metal or alkaline earth metal islithium.
 30. A method as defined in claim 25 wherein the platinum groupmetal is platinum.
 31. A method as defined in claim 25 wherein theplatinum group metal is iridium.
 32. A method as defined in claim 25wherein the platinum group metal is palladium.
 33. A method as definedin claim 25 wherein the platinum group metal is rhodium.
 34. A method asdefined in claim 25 wherein the lanthanide series component isneodymium.
 35. A method as defined in claim 25 wherein the lanthanideseries component is cerium.
 36. A method as defined in claim 25 whereinthe lanthanide series component is lanthanum.
 37. A method as defined inclaim 25 wherein the Group IVA metal is germanium.
 38. A method asdefined in claim 25 wherein the Group IVA metal is lead.
 39. A method asdefined in claim 25 wherein the Group IVA metal is tin.
 40. A method asdefined in claim 25 wherein the composite contains, on an elementalbasis, about 0.05 to about 1 wt. % platinum group metal, about 0.01 toabout 2 wt. % Group IVA metal, about 0.25 to about 3.5 wt. % alkalimetal or alkaline earth metal and an atomic ratio of lanthanide seriesmetal to platinum group metal of about 0.4:1 to about 1:1.
 41. A methodas defined in claim 25 wherein the metal contents of the catalyticcomposite is adjusted so that the atomic ratio of Group IVA metal toplatinum group metal is about 0.05:1 to about 10:1 and the atomic ratioof alkali metal or alkaline earth metal to platinum group metal is about5:1 to about 100:1.
 42. A method as defined in claim 25 wherein thecatalytic composite is sulfided in an amount sufficient to incorporateabout 0.05 to about 0.5 wt. % sulfur, calculated on an elemental basis.43. A method as defined in claim 25 wherein substantially all of theGroup IVA metal is present in the catalytic composite in the form of thecorresponding oxide.
 44. A method as defined in claim 25 whereinsubstantially all of the lanthanide series component is present in thecatalytic composite in the form of the corresponding oxide.
 45. A methodas defined in claim 25 wherein the environment contains less than 5,000wt. ppm. of H₂ O, calculated on the basis of weight of hydrocarboncharged.
 46. A method as defined in claim 25 wherein thedehydrogenatable hydrocarbon is an aliphatic hydrocarbon containing 2 to30 carbon atoms per molecule.
 47. A method as defined in claim 25wherein the dehydrogenatable hydrocarbon is a normal paraffinhydrocarbon containing about 4 to 30 carbon atoms per molecule.
 48. Amethod as defined in claim 25 wherein the dehydrogenatable hydrocarbonis a normal paraffin hydrocarbon containing about 10 to about 18 carbonatoms per molecule.
 49. A method as defined in claim 25 wherein thedehydrogenatable hydrocarbon is an alkylaromatic, the alkyl group ofwhich contains about 2 to 6 carbon atoms.
 50. A method as defined inclaim 25 wherein the dehydrogenatable hydrocarbon is a naphthene.
 51. Amethod as defined in claim 25 wherein the dehydrogenation conditionsinclude a temperature of about 700° to about 1200° F., a pressure ofabout 0.1 to about 10 atmospheres, an LHSV of about 1 to 40 hr.⁻¹, and ahydrogen to hydrocarbon mole ratio of about 1:1 to about 20:1.